Boost Converter Common Mode Noise Reduction via Impedance Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increase in switching frequency in switching power supply circuits leads to increased electromagnetic noise, particularly common mode noise in the MHz band, which is not effectively addressed by existing technologies, and results in the need for larger choke coils, hindering the downsizing of power supply circuits.
Innovation Solution
A boost converter design incorporating specific capacitors and inductors configured in a Wheatstone bridge circuit configuration, including a seventh capacitor connected between key nodes, to achieve impedance balance and reduce common mode noise without using common mode choke coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency is increased to reduce the size of passive components, then the size of passive components is reduced, but electromagnetic noise (particularly common mode noise) increases
Solution Approach 1:
The patent divides the single choke coil into multiple inductors (first inductor and second inductor) with different inductance values. This segmentation allows each inductor to handle specific frequency ranges of noise, improving noise filtering effectiveness without requiring a single large choke coil, thus resolving the contradiction between component size and noise reduction.
Solution Approach 2:
The patent introduces a capacitor connected in parallel with one of the inductors to form a resonant circuit. By adjusting the capacitance value, the resonant frequency can be tuned to target specific noise frequencies. This parameter change enables effective noise filtering at higher frequencies without increasing the physical size of the filtering components.
2Object-generated harmful factors
If the impedance of the choke coil is increased to reduce common mode noise, then common mode noise is reduced, but the size of the choke coil increases
Solution Approach 1:
Instead of using a single choke coil with high impedance, the patent segments the filtering function across multiple inductors with different inductance values. The first inductor handles lower frequency noise while the second inductor (with smaller inductance) handles higher frequency noise. This segmentation achieves effective noise filtering without requiring a single large high-impedance choke coil.
Solution Approach 2:
The patent introduces a capacitor as an intermediary element connected in parallel with one of the inductors. This capacitor-resistor-inductor combination creates a resonant circuit that acts as an impedance transformer, providing high impedance at specific noise frequencies without requiring physically large components. The intermediary capacitor enables effective noise blocking with compact dimensions.
3Object-generated harmful factors
If a common mode choke coil is used to reduce noise, then noise filtering is improved, but device complexity and cost increase
Solution Approach 1:
Instead of using a common mode choke coil that filters both differential mode and common mode noise together, the patent inverts the approach by using separate inductors with different inductance values tailored for specific frequency ranges. This inverted strategy achieves targeted noise filtering with simpler, more cost-effective components rather than a complex common mode choke coil.
Solution Approach 2:
The patent changes the parameter of inductance to have different values between the first and second inductors, rather than using identical inductors as in conventional designs. This parameter differentiation allows each inductor to be optimized for specific frequency ranges, achieving effective noise filtering without requiring expensive common mode choke coils with complex wound structures.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The problem is to contribute to downsizing while reducing common mode noise. A boost converter (100) includes a positive electrode input terminal (T1) and a negative electrode input terminal (T2), a positive electrode output terminal (T3) and a negative electrode output terminal (T4), a first positive-side wiring section (W11), a first negative-side wiring section (W12), a second positive-side wiring section (W21), a second negative-side wiring section (W22), a first capacitor (1), a first switching element (Q1), a second switching element (Q2), a first inductor (11), a second inductor (12), a second capacitor (2), a third capacitor (3), a fourth capacitor (4), a third inductor (13), a fourth inductor (14), a ground conductor member (9), a fifth capacitor (5), a sixth capacitor (6), and a seventh capacitor (7). The seventh capacitor (7) is connected between a third node (N3) and the fourth capacitor (4).